High Strength Titanium Copper Strip and Foil Having Layered Structure

ABSTRACT

A titanium copper according to the present invention contains from 1.5 to 5.0% by mass of Ti, the balance being of Cu and inevitable impurities, wherein the titanium copper has a layered structure of Cu and Ti where in a Ti concentration curve obtained by analyzing a cross section parallel to a rolling direction along a thickness direction by STEM-EDX, a lower concentration Ti layer having a Ti concentration less than an average value of Ti concentrations in the Ti concentration curve and a higher concentration Ti layer having a Ti concentration equal to or higher than the average value of the Ti concentrations in the Ti concentration curve are alternately present in the thickness direction, and wherein in the cross section parallel to the rolling direction, a number of higher concentration Ti layers is 5 layers per 500 nm in the thickness direction.

TECHNICAL FIELD

The present invention relates to a titanium copper that has improvedstrength and improved settling resistance, and is suitable for use in aconductive spring material, in particular for autofocus camera modulesand the like, a method for producing the titanium copper, a copperrolled product, an electronic device part and an autofocus cameramodule.

BACKGROUND ART

An electronic part called an autofocus camera module is used in cameralens sections for mobile phones. An autofocus function of a camera for amobile phone moves a lens in a fixed direction by spring force of amaterial used for an autofocus camera module, while moving the lens in adirection opposite to the spring force-acting direction by means ofelectromagnetic force generated by passing an electric current through acoil wound around the periphery. By such a mechanism, the camera lens isdriven to exert the autofocus function (for example, Patent Documents 1and 2).

Therefore, a copper alloy foil for use in the autofocus camera modulesrequires spring strength sufficient to withstand deformation of thematerial due to the electromagnetic force. If the spring strength islow, the material cannot withstand displacement due to theelectromagnetic force, and permanent deformation (settling) will occurso that the copper alloy foil cannot return to its initial positionafter unloading the electromagnetic force. If the settling occurs, thelens cannot move to a desired position and the autofocus function cannotbe produced, when a constant current is passed.

For the autofocus camera modules, Cu—Ni—Sn based copper alloy foilshaving a foil thickness of 0.1 mm or less and tensile strength or 0.2%yield strength of 1100 MPa or more have been used.

However, a recent demand for cost reduction has led to the use oftitanium copper foils which have relatively low raw material costs thanthe Cu—Ni—Sn based copper alloys, and the demand for the titanium copperfoil is thus increasing.

On the other hand, the strength of the titanium copper foil is lowerthan that of the Cu—Ni—Sn based copper alloy foil, causing a problemthat settling occurs. Therefore, there is a need for increasing thestrength of the titanium copper foil.

Means for increasing the strength of titanium copper includes, forexample, those described in Patent Documents 3 and 4. Patent Document 3proposes a method for producing titanium copper through the steps of asolutionizing treatment, a sub-aging treatment, cold rolling, and anaging treatment, in which a heat treatment after the solutionizingtreatment is divided into two stages, thereby increasing a range of Ticoncentration (concentration difference) due to spinodal decompositionand improving a balance between strength and bending workability. PatentDocument 4 also discloses that it is effective to increase thefluctuation of Ti concentration by a method for producing titaniumcopper through the steps of a solutionizing treatment, a preliminaryaging treatment, an aging treatment, finish rolling, and strain reliefannealing.

Other techniques for further improving the strength of titanium copperinclude those described in Patent Documents 5 to 8. Patent Document 5discloses a method of adjusting an average crystal grain size by finalrecrystallization annealing, and then carrying out cold rolling and anaging treatment in this order. Patent Document 6 discloses that coldrolling, an aging treatment and cold rolling are sequentially carriedout after a solutionizing treatment. Patent Document 7 discloses amethod of adjusting an X-ray diffraction intensity of {420} on a platesurface by sequentially carrying out hot rolling and cold rolling,followed by a solutionizing treatment in which a temperature ismaintained in a temperature range of from 750 to 1000° C. for 5 secondsto 5 minutes, and followed by cold rolling at a rolling ratio of 0 to50%, an aging treatment at 300 to 550° C. and finish cold rolling at arolling ratio of 0 to 30%. Patent Document 8 proposes a method ofadjusting a half-width of an X-ray diffraction strength of {220} on arolled surface by sequentially carrying out a first solutionizingtreatment, intermediate rolling, a final solutionizing treatment,annealing, final cold rolling, and an aging treatment underpredetermined conditions.

Further, in order to suppress generation of settling in addition toincreasing the strength, Patent Document 9 discloses a method ofcontrolling a surface roughness of a copper alloy foil by sequentiallycarrying out hot rolling and cold rolling, followed by a solutionizingtreatment, cold rolling at a rolling reduction ratio of 55% or more, anaging treatment at 200 to 450° C. and cold rolling at a rollingreduction ratio of 35% or more. Patent Document 10 discloses that aratio I(220)/I(311) is controlled by sequentially carrying out hotrolling and cold rolling, followed by a solutionizing treatment, coldrolling at a rolling reduction ratio of 55% or more, an aging treatmentat 200 to 450° C., cold rolling at a rolling reduction ratio of 50% ormore, and optionally strain relief annealing, such that the rollingreduction ratio of the cold rolling after the solutionizing treatment iscontrolled. Each of Patent Document 9 and Patent Document 10 disclosesthat the titanium copper foil can achieve 0.2% yield strength of 1100MPa or more in a direction parallel to the rolling direction.

Furthermore, Patent Document 11 proposes that Young's modulus isdecreased by carrying out hot rolling at 800 to 1000° C. to a thicknessof 5 to 20 mm, cold rolling at a working ratio of 30 to 99%,pre-annealing at a softening degree of 0.25 to 0.75 by maintenance in atemperature range of from 500 to 650° C. for 5 to 80 seconds at anaverage temperature rising rate of 400 to 500° C. of 1 to 50° C./sec,cold rolling at a working ratio of 7 to 50%, a solutionizing treatmentat 700 to 900° C. for 5 to 300 seconds, and an aging treatment at 350 to550° C. for 2 to 20 hours.

Further, as a technique focusing on structural control, Patent Document12 discloses a method of improving a balance between strength andconductivity by subjecting a titanium copper having a compositioncontaining Ti in a range of 0.5% by mass or more and 3.5% by mass orless, the balance being Cu and inevitable impurities, to finish cold orhot rolling at a rolling reduction ratio of more than 90% and an agingtreatment to form a lamellar structure after the aging treatment.

PRIOR ART DOCUMENT

-   Patent Document 1: Japanese Patent Application Publication No.    2004-280031 A-   Patent Document 2: Japanese Patent Application Publication No.    2009-115895 A-   [Patent Document 3: Japanese Patent Application Publication No.    2015-098622 A-   Patent Document 4: Japanese Patent Application Publication No.    2015-127438 A-   Patent Document 5: Japanese Patent No. 4001491 B-   Patent Document 6: Japanese Patent No. 4259828 B-   Patent Document 7: Japanese Patent Application Publication No.    2010-126777 A-   Patent Document 8: Japanese Patent Application Publication No.    2011-208243 A-   Patent Document 9: Japanese Patent No. 5723849 B-   Patent Document 10: Japanese Patent No. 5526212 B-   Patent Document 11: Japanese Patent Application Publication No.    2014-074193 A-   Patent Document 12: Japanese Patent Application Publication No.    2014-173145 A

SUMMARY OF INVENTION Problem to be Solved by the Invention

Main objects of Patent Documents 3 and 4 are to improve the strength andbending workability of the titanium copper, but these documents do notfocus on the problem of settling. In addition, the titanium copperdescribed in each of Patent Document 3 and Patent Document 4 has astrength of about 900 to 1200 MPa, so that it may not be used inapplications that require high strength such as autofocus modules.

In some Examples and Comparative Examples described in thespecifications of Patent Documents 5 to 8, some titanium copper having a0.2% proof stress of 1100 MPa or more can be found. However, the presentinventors have found that the conventional techniques proposed in PatentDocuments 5 to 8 causes settling when a material is loaded, deformed andthen unloaded, so that only high strength cannot allow the use of thetitanium copper as a conductive spring material for autofocus cameramodules or the like.

Patent Documents 9 to 11 focus on the problem of settling and propose amethod of suppressing the generation of settling. However, it has beenfound that in the proposed techniques of Patent Documents 9 to 11, thefoil having a relatively thin thickness does not produce effects enoughto be expected. That is, it has been found that although the proposedtechniques of Patent Documents 9 to 11 produce a significant effect forthe foil having somewhat thick foil thickness, the foil having a thinnerthickness does not produce a sufficient effect to be expected from thefoil having the thicker foil thickness.

Further, Patent Document 12 mentions that the strength increases due tothe lamellar structure. However, the titanium copper described in PatentDocument 12 may have a low strength and may be broken in applicationsrequiring higher strength, which will cause a problem that the titaniumcupper will not function as a spring. Therefore, it is not appropriatein terms of achieving both strength and settling suppression.

An object of the present invention is to solve such problems, and is toprovide a titanium copper that has required high strength when used as aspring, has decreased settling and is used as a conductive springmaterial employed for electronic device components such as autofocuscamera modules, a method for producing the titanium copper, a copperrolled product, an electronic device part and an autofocus cameramodule.

Means for Solving the Problem

As a result of studies for effects of a metal structure on settling, thepresent inventors have found that a certain fine layered structure of Cuand Ti in the metal structure is effective for suppressing settling andincreasing the strength. Further, the present inventors have found thatsuch a fine layered structure of Cu and Ti can be obtained by adjustinga solidification rate during casting.

Based on such findings, a titanium copper according to the presentinvention contains from 1.5 to 5.0% by mass of Ti, the balance being ofCu and inevitable impurities, wherein the titanium copper has a layeredstructure of Cu and Ti where in a Ti concentration curve obtained byanalyzing a cross section parallel to a rolling direction along athickness direction by STEM-EDX, a lower concentration Ti layer having aTi concentration less than an average value of Ti concentrations in theTi concentration curve and a higher concentration Ti layer having a Ticoncentration equal to or higher than the average value of the Ticoncentrations in the Ti concentration curve are alternately present inthe thickness direction, and wherein in the cross section parallel tothe rolling direction, a number of higher concentration Ti layers is 5layers per 500 nm in the thickness direction.

Here, in the titanium copper according to the present invention, thenumber of the higher concentration Ti layers is from 5 to 100 layers per500 nm in the thickness direction.

The titanium copper according to the present invention preferably has atensile strength of 1100 MPa or more in the direction parallel to therolling direction.

The titanium copper according to the present invention further maycontain one or more elements selected from Ag, B, Co, Fe, Mg, Mn, Mo,Ni, P, Si, Cr and Zr in a total amount of from 0 to 1.0% by mass.

The present invention also provides a copper rolled product comprisingany one of the titanium copper as described above.

The present invention further provides an electronic device partcomprising any one of the titanium copper as described above. It ispreferable that the electronic device part is an autofocus cameramodule.

The present invention further provides an autofocusing camera modulecomprising: a lens; a spring member for elastically biasing the lens toan initial position in an optical axis direction; and an electromagneticdriver configured to generate electromagnetic force for withstanding thebiasing force of the spring member so that the lens can be driven in theoptical axis direction, wherein the spring member comprises any one ofthe titanium copper as described above.

Effects of the Invention

According to the present invention, it is possible to obtain a Cu—Tibased alloy having high strength and decreased settling, which can besuitably used as a conductive spring material for use in electronicdevice parts such as autofocus camera modules.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a Ti mapping view obtained by performing STEM-EDX analysis ona cross section parallel to a rolling direction of titanium copperaccording to one embodiment of the present invention.

FIG. 2 is a schematic view of a graph showing a Ti concentration curvein a thickness direction of a cross section parallel to a rollingdirection, which is obtained by performing line analysis with STEM-EDXon a cross section parallel to the rolling direction of titanium copperaccording to one embodiment of the present invention.

FIG. 3 is a Ti mapping view obtained by performing STEM-EDX analysis ona cross section parallel to a rolling direction of conventional titaniumcopper.

FIG. 4 is a cross-sectional view showing an autofocus camera moduleaccording to the present invention.

FIG. 5 is an exploded perspective view of the autofocus camera module inFIG. 4.

FIG. 6 is a cross-sectional view showing the operation of the autofocuscamera module in FIG. 4.

FIG. 4 shows an example of measurement results of a solder adhesivestrength test.

FIG. 7 is a schematic view showing a method for measuring an amount ofsettling.

MODES FOR CARRYING OUT THE INVENTION

A titanium copper according to the present invention contains from 1.5to 5.0% by mass of Ti, the balance being of Cu and inevitableimpurities, and is in the form of a foil or strip. The titanium copperhas a layered structure of Cu and Ti where in a Ti concentration curveobtained by analyzing a cross section parallel to a rolling directionalong a thickness direction by STEM-EDX, a lower concentration Ti layerhaving a Ti concentration less than an average value of Ticoncentrations in the Ti concentration curve and a higher concentrationTi layer having a Ti concentration equal to or higher than the averagevalue of the Ti concentrations in the Ti concentration curve arealternately present. In the cross section parallel to the rollingdirection, a number of the higher concentration Ti layers is 5 layersper 500 nm in the thickness direction.

(Ti Concentration)

The titanium copper according to the present invention has a Ticoncentration of from 1.5 to 5.0% by mass. For the titanium copper, thestrength and conductivity is increased by allowing solid solution of Tiinto the Cu matrix with a solutionizing treatment and then dispersingfine precipitates in the alloy with an aging treatment.

If the Ti concentration is less than 1.5% by mass, the precipitation ofprecipitates will become insufficient and the desired strength cannot beobtained. If the Ti concentration exceeds 5.0% by mass, the workabilitywill deteriorate and the material will be easily cracked during rolling.In view of the balance between the strength and the workability, the Ticoncentration may be preferably from 2.5 to 4.5% by mass.

(Other Additive Elements)

The strength of the titanium copper according to one embodiment of thepresent invention can be further improved by containing one or more ofAg, B, Co, Fe, Mg, Mn, Mo, Ni, P, Si, Cr, and Zr in the total amount offrom 0 to 1.0% by mass. The total content of these elements may be zero,that is, these elements may not be contained. The reason why the upperlimit of the total content of these elements is 1.0% by mass is that ifit is more than 1.0% by mass, the workability is deteriorated and thematerial is easily cracked during rolling. In view of the balancebetween strength and workability, it is preferable to contain the aboveelements in the total amount of from 0.005 to 0.5% by mass.

(Tensile Strength)

The titanium copper according to the present invention can achieve atensile strength in a direction parallel to a rolling direction of 1100MPa or more, or even 1200 MPa or more. The tensile strength in thedirection parallel to the rolling direction of 1200 MPa or more is adesirable characteristic for use as a conductive spring material forautofocus camera modules. In a preferred embodiment, both of tensilestrengths in the direction parallel to the rolling direction and thedirection perpendicular to the rolling direction are 1300 MPa or more,and in a more preferred embodiment, both are 1400 MPa or more.

On the other hand, the upper limit of the tensile strength is notparticularly limited in terms of the strength intended by the presentinvention, but the tensile strengths in the directions parallel andperpendicular to the rolling direction are generally 2000 MPa or less,and typically 1800 MPa or less, taking labor and costs into account.

In the present invention, the tensile strength of the titanium copper inthe direction parallel to the rolling direction is measured inaccordance with JIS Z2241: 2011 (Metal Material Tensile Test Method).

(Layered Structure of Cu and Ti)

As illustrated in FIGS. 1 and 2, when performing analysis on the crosssection in the direction parallel to the rolling direction by an energydispersive X-ray spectroscopy (EDX) with a scanning transmissionelectron microscope (STEM) (STEM-EDX analysis), the titanium copperaccording to an embodiment of the present invention has a layeredstructure of Cu and Ti in which a lower concentration Ti layer having aTi concentration less than an average concentration and a higherconcentration Ti layer having a Ti concentration equal to or higher thanthe average concentration are alternately present in the thicknessdirection (the up and down direction in FIG. 1), in the cross sectionparallel to the rolling direction.

The stable and continuous presence of such a layered structure of Cu andTi in the cross section parallel to the rolling direction enhancesresistance to deflection and makes it difficult to generate permanentdeformation, so that it would allow settling to be effectivelysuppressed even if the copper foil has a thin thickness of 0.1 mm orless, although this invention is not limited to such a theory.

The “layered structure” is defined as a structure in which the lowerconcentration Ti layer and the higher concentration Ti layer arealternately present, and each layer is continuous over 50 nm or more inthe rolling direction. A structure having a length less than 50 nm inthe rolling direction is defined as a speckled structure.

On the other hand, as shown in FIG. 3, the conventional titanium copperhas a discontinuous and speckled distribution of a portion having ahigher Ti concentration and a portion having a lower Ti concentration inthe cross section parallel to the rolling direction, and hassubstantially uniform peak values for Ti concentrations in the thicknessdirection. In this case, the titanium copper having a thinner thicknesshas a discontinuous structure. Therefore, it does not have strongresistance against deflection, and easily generates permanentdeformation within the elastic limit, so that the settling would besufficiently suppressed.

Further, as an index representing the layered structure of Cu and Ti, anumber of layers of each of the lower concentration Ti layer and thehigher concentration Ti layer in the thickness direction can be defined.This analysis is also performed by STEM-EDX analysis. When linearanalysis of a cross section parallel to the rolling direction isperformed by STEM-EDX in the thickness direction, the Ti concentrationat each measurement point varies depending on the Ti concentration. Inthe present invention, the Ti concentration is observed per one visualfield (at magnifications of 1,000,000; observation visual field: 140nm×140 nm), and a Ti concentration curve with respect to a distance inthe thickness direction is obtained as shown in FIG. 2. The higherconcentration Ti layer and the lower concentration Ti layer in the Ticoncentration curve are applied mutatis mutandis by replacing thecontour curve for the surface properties as defined in JIS B0601 withthe Ti concentration curve. That is, the higher concentration Ti layeris defined as an upper portion where the Ti concentration becomes higherthan the average value of the Ti concentration curve, among curveportions sandwiched between adjacent two intersections in an X axisdirection when the Ti concentration curve is divided by an X axis(average values in the Ti concentration curve). Also, the lowerconcentration Ti layer is defined as a lower portion where the Ticoncentration becomes lower than the average value of the Ticoncentration curve, among curve portions sandwiched between adjacenttwo intersections in an X axis direction when the Ti concentration curveis divided by an X axis (average values in the Ti concentration curve).

Then, the number of the respective layers at 100 nm is measured, and themeasurement is repeated five times while shifting in the thicknessdirection, and the five measured values are summed to obtain the numberof layers per unit measurement distance (500 nm). The measurement andcalculation of the number of layers per unit measurement distance arerepeated three times, and average values of the three measurements aredefined as “a number of lower concentration Ti layers” and “a number ofhigher concentration Ti layers”, respectively. It should be noted thatsince the layered structure of Cu and Ti is exhibited in parallel to therolling direction, the above line analysis is necessarily performed inthe thickness direction of the titanium copper.

As described above, when analyzing and measuring the cross sectionparallel to the rolling direction with STEM-EDX, the titanium copperaccording to the present invention has a number of higher concentrationTi layers of 5 layers or more, more preferably 10 layers or more, evenmore preferably 20 layers or more per 500 nm, in the cross sectionparallel to the rolling direction. If the number of higher concentrationTi layers is too low, it will be difficult to achieve both strength andsettling suppression. On the other hand, although there is no demeritdue to the number of layers being too high, if the number of layersexceeds a certain level, the effect of increasing strength orsuppressing settling tends to be saturated. Therefore, the number oflayers should be controlled between 5 and 100 layers.

(Thickness of Titanium Copper)

The titanium copper according to the present invention has a thicknessof, for example, 0.1 mm or less, and in a typical embodiment, athickness of from 0.018 mm to 0.08 mm, and in a more typical embodiment,a thickness of from 0.02 mm to 0.06 mm.

(Production Method)

To produce the titanium copper as described above, raw materials such aselectrolytic copper and Ti are first melted in a melting furnace toobtain a molten metal having a desired composition. The molten metal isthen fed to a casting space of a mold where the molten metal is castinto an ingot. In order to prevent oxidative wear of titanium, themelting and casting are preferably carried out in a vacuum or in aninert gas atmosphere.

Here, in order to obtain the above layered structure of Cu and Ti of thetitanium copper, it is important to adjust a ratio of a thickness of aperipheral wall portion surrounding a molding space of a mold to athickness of an ingot (also referred to as a “mold/ingot thicknessratio). By adjusting the ratio, a cooling rate of the ingot can becontrolled.

The mold/ingot thickness ratio can be changed as needed to obtain thedesired structure. In order to achieve improved strength and settlingresistance based on the layered structure of Cu and Ti, the mold/ingotthickness ratio is preferably 0.5 or more, particularly preferably 1.0or more. The upper limit of the mold/ingot thickness ratio is notparticularly set. However, the effect is saturated even if themold/ingot thickness ratio is too high, so the mold/ingot thicknessratio is generally preferably 8.0 or less.

The thickness of the peripheral wall portion of the mold is measuredalong a direction parallel to the thickness of the ingot.

A suitable material of the peripheral wall portion of the mold can berefractory brick. Conventionally, cast iron or copper has been used asthe material of the peripheral wall portion of the mold. However, byreplacing this with the refractory brick, a cooling rate after feedingthe molten metal can be reduced, thereby allowing slow cooling of theingot.

Typically, the ingot is then subjected to hot rolling, cold rolling 1, asolutionizing treatment, cold rolling 2, an aging treatment, coldrolling 3, and strain relief annealing in this order to finish the ingotin the form of a foil or strip having desired thickness and properties.However, the cold rolling 3 and/or the strain relief annealing may beomitted depending on circumstances.

The hot rolling and the subsequent cold rolling may be carried out underconventional conditions used in the production of the titanium copper,and there are no special requirements herein. The solutionizingtreatment may be carried out under conventional conditions, for example,at 700 to 1000° C. for 5 seconds to 30 minutes.

To obtain high strength, the cold rolling 2 can be carried out after thesolutionizing treatment. The rolling reduction ratio of the cold rolling2 is preferably 90% or more, and more preferably 95% or more. If therolling reduction ratio is less than 90%, it will be difficult to obtaina tensile strength of 1100 MPa or more. The upper limit of the rollingreduction ratio is not particularly limited from the viewpoint of thestrength intended by the present invention, but it does not industriallyexceed 99.8%.

The aging treatment is carried out at a temperature of from 200 to 450°C. for a heating time of from 2 hours to 20 hours. If the heatingtemperature is lower than 200° C. or higher than 450° C., it will bedifficult to obtain a tensile strength of 1100 MPa or more. If theheating time is less than 2 hours or more than 20 hours, it will bedifficult to obtain a tensile strength of 1100 MPa or more.

Depending on the intended strength, the cold rolling 3 can be carriedout after the aging treatment. The rolling reduction ratio of the coldrolling 3 is preferably 35% or more, more preferably 50% or more, andstill more preferably 70% or more. In addition, when the cold rolling 3is unnecessary, it can also be omitted.

Further, according to the purpose such as removal of residual strain,the cold rolling 3 can be followed by strain relief annealing at 200 to500° C. for 1 to 5 minutes. When the strain relief annealing isunnecessary, it also can be omitted.

In general, after the heat treatment, the surface may be washed with anacid or polished to remove an oxide film or an oxide layer formed on thesurface. In the present invention, the surface also can be washed withan acid or polished after the heat treatment.

(Application)

The titanium copper according to the present invention can be suitablyused as a material for electronic device parts, including, but notlimited to, switches, connectors, jacks, terminals and relays, inparticular as a conductive spring member for use in electronic deviceparts such as autofocus camera modules.

In one embodiment, the autofocus camera module includes: a lens; aspring member for elastically biasing the lens to an initial position inan optical axis direction; and an electromagnetic drive means configuredto generate electromagnetic force for withstanding the biasing force ofthe spring member so that the lens can be driven in the optical axisdirection. By way of example, the electromagnetic driving meansincludes: a U-shaped cylindrical yoke; a coil housed inside an innerperipheral wall of the yoke; and a magnet enclosing the coil and housedinside the outer peripheral wall of the yoke.

FIG. 4 is a cross-sectional view showing an example of the autofocuscamera module according to the present invention, FIG. 5 is an explodedperspective view of the autofocus camera module in FIG. 4, and FIG. 6 isa cross-sectional view showing the operation of the autofocus cameramodule in FIG. 4.

An autofocus camera module 1 includes: a U-shaped cylindrical yoke 2; amagnet 4 attached to an outer wall of the yoke 2; a carrier 5 providedwith a lens 3 in a central position; a coil 6 attached to the carrier 5;a base 7 to which the yoke 2 is attached; a frame 8 supporting the base7; two spring members 9 a, 9 b for supporting the carrier 5 at the upperand lower positions; and two caps 10 a, 10 b covering these upper andlower positions. These two spring member 9 a, 9 b are the same articles,and support the carrier 5 by holding it from the upper and lowerpositions in the same positional relationship, while functioning as apower supply route to the coil 6. The carrier 5 moves upward by applyingan electric current to the coil 6. It should be noted that the wordings“upper” and “lower” are used herein as needed, and they refer to upperand lower in FIG. 4 and the upper represents a positional relationshipthat is directed from the camera to a subject.

The yoke 2 is a magnetic material such as soft iron, and assumes aU-shaped cylindrical shape whose upper surface portion is closed, andhas cylindrical inner wall 2 a and outer wall 2 b. A ring-shaped magnet4 is attached (adhered) to the inner surface of the U-shaped outer wall2 b.

The carrier 5 is a molded product made of a synthetic resin or the like,which has a cylindrical structure with a bottom portion, and the carrier5 supports the lens in the central position, and binds the pre-formedcoil 6 onto the bottom surface outwardly so that the coil 6 is mountedthereon. The yoke 2 is integrated by fitting it to the inner peripheryof the base 7 which is a rectangular resin molded article, and the wholeyoke 2 is further secured by the frame 8 which is a resin moldedarticle.

The spring members 9 a, 9 b are fixed by holding their outermostperipheral portions by the frame 8 and the base 7, respectively, and thecutout grooves arranged per 120° on the inner peripheral portion arefitted to the carrier 5 and fixed by thermal caulking or the like.

The spring member 9 b and the base 7 as well as the spring member 9 aand the frame 8 are fixed by adhesive and thermal caulking,respectively, and further the cap 10 b is attached to the bottom surfaceof the base 7, and the cap 10 a is attached to the upper portion of theframe 8, and the spring member 9 b is sandwiched between the base 7 andthe cap 10 b and the spring member 9 a is sandwiched between the frame 8and the cap 10 a, so that they are adhered.

The lead wire of one of the coils 6 is extended upward passing throughthe groove provided on the inner peripheral surface of the carrier 5,and soldered to the spring member 9 a. The other lead wire is extendeddownward passing through the groove provided on the bottom surface ofthe carrier 5, and soldered to the spring member 9 b.

The spring members 9 a, 9 b are plate springs made of the titaniumcopper according to the present invention. They have spring propertiesand elastically energize the lens 3 to the initial position in theoptical axis direction. At the same time, they also act as power supplypaths to the coil 6. One position on the outer peripheral portion ofeach of the spring members 9 a, 9 b projects outward, thereby acting asa power supply.

The cylindrical magnet 4 is magnetized in the radial (diameter)direction and forms a magnetic path passing through an inner wall 2 a,an upper surface portion and an outer wall 2 b of the U-shaped yoke 2,and the coil 6 is disposed in the gap between the magnet 4 and the innerwall 2 a.

The spring members 9 a, 9 b have the same shape, and are attached in thesame positional relationship as shown in FIGS. 4 and 5, so that anyaxial deviation can be suppressed when the carrier 5 is moved upward.Since the coil 6 is manufactured by pressure molding after winding, theaccuracy of the finished outer diameter of the coil can be improved,thereby allowing the coil to be easily arranged in a predeterminednarrow gap. The carrier 5 is butted to the base 7 at the lowest positionand butted to the yoke 2 at the uppermost position, and it will be thusequipped with the butting mechanisms in the upper and bottom verticaldirection, thereby preventing any detachment.

FIG. 6 shows a sectional view when upwardly moving the carrier 5 havingthe lens 3 for the autofocus by applying an electric current to the coil6. When a voltage is applied to the power supply terminals of the springmembers 9 a, 9 b, the electric current flows through the coil 6, and theupward electromagnetic force acts on the carrier 5. On the other hand,restoring force of two linked spring members 9 a, 9 b downwardly acts onthe carrier 5. Therefore, the distance of upward movement of the carrier5 will be a position where the electromagnetic force and the restoringforce are balanced. This will allow determination of the moving amountof the carrier 5 according to the amount of the electric current appliedto the coil 6.

Since the upper spring member 9 a supports the upper surface of thecarrier 5 and the lower spring member 9 b support the lower surface ofthe carrier 5, the restoring force will equally work downward on theupper and lower surfaces of the carrier 5, so that any axialdisplacement of the lens 3 can be suppressed.

Therefore, for the upward movement of the carrier 5, no guide by ribsand the like is needed and used. Since there is no sliding friction bythe guide, the amount of movement of the carrier 5 will be purelycontrolled by the balance between the electromagnetic force and therestoring force, thereby achieving the smooth and accurate movement ofthe lens 3. This will achieve autofocusing with reduced blurring of thelens.

It should be noted that although the magnet 4 has been described as onehaving the cylindrical shape, the magnet is not limited to this shape,and may be divided 3 to 4 parts and magnetized in the radial direction,which may be fixed by adhering to the inner surface of the outer wall 2b of the yoke 2.

Examples

Hereinafter, Examples of the present invention will be illustrated, butthese Examples are presented in order to provide better understanding ofthe present invention and its advantages, and in no way intended tolimit the present invention.

Each alloy containing the alloy components shown in Table 1, the balancebeing copper and inevitable impurities, was used as an experimentalmaterial, and effects of the alloy components and production conditionson tensile strength and settling were studied.

<Production Conditions>

First, 2.5 kg of electrolytic copper was melted in a vacuum meltingfurnace, and alloy elements were added such that each alloy compositionas shown in Table 1 was obtained. The molten metal was cast into a moldas shown below to produce an ingot having a thickness of 30 mm, a widthof 60 mm, and a length of 120 mm. The ingot was processed in thefollowing step order to produce each product sample having thepredetermined thickness as shown in Table 1.

(1) Melting Casting: The casting temperature was 1300° C., the mold wasselected from refractory brick, cast iron, and copper, and the coolingrate during casting was changed. The cooling rate is higher in the orderof copper, cast iron, and refractory brick. The mold/ingot thicknessratio was as shown in Table 1.

(2) Hot Rolling: The above ingot was further heated at 950° C. for 3hours and rolled to a thickness of 10 mm.

(3) Grinding: The oxide scale produced in hot rolling was removed by agrinder. The thickness after grinding was 9 mm.

(4) Cold rolling 1: The ingot was rolled to a predetermined thicknessdepending on the rolling reduction ratio.

(5) Solutionizing Treatment: The sample was charged with an electricfurnace 1 heated to 800° C. and maintained for 5 minutes, and the samplewas quenched by placing it in a water bath.

(6) Cold Rolling 2: With regard to the sample that did not carry out thecold rolling 3 below, it was rolled at the rolling reduction ratio asshown in Table 1 to the product thickness as shown in Table 1.

(7) Aging Treatment: The sample was heated in an Ar atmosphere under theconditions as shown in Table 1.

(8) Cold Rolling 3: With regard to the sample that carried out the coldrolling 3, it was rolled at the rolling reduction ratio as shown inTable 1 to the product thickness as shown in Table 1. In addition, thesample that did not carried out the cold rolling 3 was indicated as “-”.

(9) Strain Relief Annealing: After carrying out the cold rolling 2 orthe cold rolling 3, the sample was placed in an electric furnace heatedto 400° C. and maintained for 10 seconds, and the sample was then placedin a water bath and rapidly cooled. Table 1 shows the temperature andtime of the strain relief annealing for the samples subjected to thestrain relief annealing, and indicates the sample that did not carriedout it as “-”.

The following evaluations were performed for each product sampleproduced as described above.

<Tensile Strength>

The tensile strength in the direction parallel to the rolling directionwas measured in accordance with JIS Z2241: 2011 using a tensile testeraccording to the measurement method as described above.

<Settling>

Each strip sample having a width of 15 mm and a length of 25 mm wascollected such that the longitudinal direction was parallel to therolling direction, and, as shown in FIG. 7, one end of the sample wasfixed, and a punch with a tip processed into a knife edge was pressed ata moving rate of 1 mm/min at a position of a distance L from that fixedend to provide the sample with deflection of the distance d. The punchwas then returned to its initial position and unloaded. After unloading,an amount of settling δ was determined.

The test conditions were L=3 mm and d=2 mm when the foil thickness ofthe sample was 0.05 mm or less, and L=5 mm and d=4 mm when the foilthickness was thicker than 0.05 mm. Further, the amount of settling wasmeasured at a resolution of 0.01 mm, and when the settling was notdetected, it was expressed as <0.01 mm.

<Structural Analysis>

As described above, the cross section parallel to the rolling directionwas observed with STEM-EDX, and it was judged whether the structure waslayered or speckled from the resulting image. The scanning transmissionelectron microscope used herein was JEM-2100F from JEOL, and themeasurement conditions were a sample tilt angle of 0° and anacceleration voltage of 200 kV.

Further, the cross section parallel to the rolling direction wassubjected to line analysis in the thickness direction by STEM-EDX, andthe Ti concentration curve with respect to the distance in the thicknessdirection was obtained.

TABLE 1 Cold Casting Condition Rolling 2 Product Component Mold/IngotWorking Thickness Sub- Thickness Ratio mm Ti component Mold Ratio (%)Example 1 0.03 3.2 — Refractory Brick 0.5 98 Example 2 0.03 3.2 —Refractory Brick 0.7 98 Example 3 0.03 3.2 — Refractory Brick 0.9 98Example 4 0.03 3.2 — Refractory Brick 1.0 98 Example 5 0.03 3.2 —Refractory Brick 3 98 Example 6 0.03 3.2 — Refractory Brick 4 98 Example7 0.03 3.2 Refractory Brick 6 98 Example 8 0.03 3.2 — Refractory Brick 898 Example 9 0.018 3.2 — Refractory Brick 1 98 Example 10 0.05 3.2 —Refractory Brick 1 98 Example 11 0.1 3.2 — Refractory Brick 1 98 Example12 0.03 4.0 — Refractory Brick 1 98 Example 13 0.03 3.2 0.2% FeRefractory Brick 1 98 Example 14 0.03 3.2 0.1% Ag + Refractory Brick 198 0.1% Co − 0.1% Ni Example 15 0.03 3.2 0.05% Si − Refractory Brick 198 0.1% Ni − 01.% Zr − 0.1% Mg Example 16 0.03 3.2 0.05% B − RefractoryBrick 1 98 0.5% Mo − 0.4% Cr Example 17 0.03 3.2 — Refractory Brick 1 98Example 18 0.03 3.2 — Refractory Brick 1 98 Comparative 0.03 3.2 —Refractory Brick 0.3 98 Example 1 Comparative 0.03 3.2 — RefractoryBrick 0.4 98 Example 2 Comparative 0.03 3.2 — Cast Iron 2 98 Example 3Comparative 0.03 3.2 — Copper 2 98 Example 4 Comparative 0.03 1.4 —Refractory Brick 2 98 Example 5 Comparative 0.03 5.1 — Refractory Brick2 Cracking Occurred Example 6 during Hot Rolling Comparative 0.03 3.20.1 Si + Refractory Brick 2 Cracking Occurred Example 7 0.2 Ni + duringHot Rolling 0.5 Zr + 0.5 Mg Number of Higher Concentration Cold TiLayers/ Rolling 3 500 nm Working Stress (* Average Tensile Ratio Reliefat 3 Strength Settling (%) Annealing Structure positions) (MPa) (mm)Example 1 — — Layered 5.1 1322 <0.01 Example 2 Layered 7.0 1333 <0.01Example 3 Layered 9.0 1350 <0.01 Example 4 — — Layered 13.2 1364 <0.01Example 5 — — Layered 20.4 1382 <0.01 Example 6 — — Layered 25.6 1444<0.01 Example 7 — — Layered 50.4 1460 <0.01 Example 8 — — Layered 100.21470 <0.01 Example 9 — — Layered 15.3 1450 <0.01 Example 10 — — Layered14.8 1423 <0.01 Example 11 — — Layered 13.0 1390 <0.01 Example 12 — —Layered 18.2 1520 <0.01 Example 13 — — Layered 13.0 1450 <0.01 Example14 — — Layered 14.0 1430 <0.01 Example 15 — — Layered 14.2 1425 <0.01Example 16 — — Layered 15.0 1407 <0.01 Example 17 78 — Layered 14.7 13270.05 Example 18 78 400° C. × Layered 14.2 1355 0.03 10 sec Comparative —— Layered 1.9 1320 0.08 Example 1 Comparative — — Layered 2.2 1350 0.07Example 2 Comparative — — Speckled — 1350 0.12 Example 3 Comparative — —Speckled — 1300 0.12 Example 4 Comparative — — Layered 1.2 800 1 Example5 Comparative Cracking Occurred during Hot Rolling Example 6 ComparativeCracking Occurred during Hot Rolling Example 7

In each of Examples 1 to 16, the refractory brick was used, and themold/ingot ratio was adjusted, whereby the number of higherconcentration Ti layers was 5 or more, and both high strength andsuppression of settling were achieved.

In each of Comparative Examples 1 and 2, the layered structure wasobtained, but the mold was thin and the ingot was rapidly cooled, sothat the number of higher concentration Ti layers was lower and settlingoccurred.

In Comparative Example 3 and Comparative Example 4, the ingot wasrapidly cooled due to the material of the mold, so that the structurewas not layered and settling occurred.

In Comparative Example 5, the Ti concentration of the matrix phase waslower, so that the strength was lower and settling occurred.

In Comparative Example 6, the titanium concentration was more than 5%,so that cracking occurred during hot rolling, and the sample could notbe prepared, and strength and settling could not be measured.

In Comparative Example 7, the total content of the sub-components wasmore than 1.0%, so that cracking occurred during hot rolling, and thesample could not be prepared, and strength and settling could not bemeasured.

1. A titanium copper containing from 1.5% to 5.0% by mass of Ti, thebalance being of Cu and inevitable impurities, wherein the titaniumcopper has a layered structure of Cu and Ti where in a Ti concentrationcurve obtained by analyzing a cross section parallel to a rollingdirection along a thickness direction by STEM-EDX, a lower concentrationTi layer having a Ti concentration less than an average value of Ticoncentrations in the Ti concentration curve and a higher concentrationTi layer having a Ti concentration equal to or higher than the averagevalue of the Ti concentrations in the Ti concentration curve arealternately present in the thickness direction, and wherein in the crosssection parallel to the rolling direction, a number of higherconcentration Ti layers is 5 layers per 500 nm in the thicknessdirection.
 2. The titanium copper according to claim 1, wherein thenumber of higher concentration Ti layers is from 5 lavers to 100 layersper 500 nm in the thickness direction.
 3. The titanium copper accordingto claim 1, wherein the titanium copper has a tensile strength of 1100MPa or more in a direction parallel to the rolling direction.
 4. Thetitanium copper according to claim 1, wherein the titanium copperfurther contains one or more elements selected from the group consistingof Ag, B, Co, Fe, Mg, Mn, Mo, Ni, P, Si, Cr, and Zr in a total amount offrom 0 to 1.0% by mass.
 5. An electronic device part comprising thetitanium copper according to claim
 1. 6. The electronic device partaccording to claim 5, wherein the electronic device part is an autofocuscamera module.
 7. An autofocusing camera module comprising: a lens; aspring member for elastically biasing the lens to an initial position inan optical axis direction; and an electromagnetic driver configured togenerate electromagnetic force for withstanding the biasing force of thespring member so that the lens can be driven in the optical axisdirection, wherein the spring member comprises the titanium copperaccording to claim 1.